It is fashionable these days to blame almost everything on man-made global warming. So it comes as no great surprise to read in a recent New York Times story that leads of open water in ice fields near the North Pole filled cruise passengers on a Russian icebreaker with a sense of alarm about impending climate disasters. Two scientists-lecturers aboard, a Harvard zoologist and an American Museum paleontologist (experts on animals and fossils, but not on meteorology) were shocked, as ABC News reported, to find Santas workshop underwater.

I am a veteran of two Arctic expeditions with the US Navy, and I can testify that icebreakers always search for leads to make their way through the ice. After a long summer of 24-hour days it is not unusual to find open leads all over the place, especially after strong winds break up the winter ice.

Nor is this a recent phenomenon. In a 1969 Dutch atlas the following passage appears: The Northern Ice Sea is never completely frozen; 3- to 30-meter thick ice floes continue moving slowly around the pole. At the North Pole the winter temperature is never lower than -35 degrees Celsius. Summer temperatures can rise to 10 to 12 degrees Celsius. Those last temperatures are well above freezing.

But all this proves little about climate change or about enhanced greenhouse warming. For this purpose we use instruments: thermometers at weather stations, radiosondes carried into the atmosphere by weather balloons twice daily and, of course, Earth-circling weather satellites, that sense atmospheric temperatures remotely. And all of these agree that the polar regions have not warmed appreciably in recent decades.

Climate models do call for a warming trend as levels of atmospheric carbon dioxide rise because of the burning of fossil fuels. Hence the dilemma: Do we believe theoretical models of the atmosphere or the atmosphere itself? I prefer to believe in the atmosphere and the actual observations that show no current warming. If this clashes with the accepted popular wisdom and media hype, so be it. I go with published data.

The Earth did warm between about 1900 and 1940, with the climate recovering from a previous cold period that climate experts refer to as the Little Ice Age. As a result of these changes, which have nothing to do with human influences, it is warmer now than it was 100 years ago. This has had an influence on polar ice, which has been slowly thinning, as it melts from beneath. And the ice will continue to thin for some time to come even though the climate is no longer warming. Moral: It takes a lot of time to melt ice.

Weather satellites tell us that polar ice cover is shrinkinglikely a delayed effect of the pre-1940 warming. The Northeast Passage has opened up, allowing ships to sail from London to Japan along the coast of Siberia. Its all part of a natural climate cycle and need not cause concern. Recall that 1000 years ago the climate was so warm that Vikings settled Greenland and grew crops there for a few centuries. Just imagine: Santas reindeers would have had to swim to get here from the North Pole.